I recently got around to setting up OIDC for my internal apps using Pocket ID.
Sonarr v5 adds OIDC support, currently only in beta
Jellyfin SSO plugin
Nextcloud with the Nextcloud OIDC app
Mealie, Paperless, and Immich natively support OIDC
Calibre-Web I migrated to AutoCaliWeb, which supports generic OIDC
Sadly Navidrome doesn't natively support OIDC and forward auth is a bit jank due to the subsonic API